<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>标签，类，id选择器</title>
    <style>
        p {
            background: #ff0000;
        }
        #main {
            background: #00ff00;
        }
        .dclass {
            background: #0000ff;
        }
    </style>
</head>
<body>
    <p>标签选择器</p>
    <div id="main">id选择器</div>
    <div class="dclass">class选择器</div>
</body>
</html>